The invention relates to a connector for a fuel pump in a motor vehicle, in order to allow the fuel pump to make contact with the electrical supply lines. As a rule, such fuel pumps are arranged in the fuel tank in the motor vehicle, in order to feed the fuel from the fuel tank to the internal combustion engine.
Known fuel pumps have one or two pump stages, which are driven by an electric motor. The known fuel pumps are in this case designed such that the pump stage is arranged at the lower end in a physical mounting for the fuel pump. The pump stage is connected to an electric motor, and a bearing plate together with the connector (which is arranged outside the housing of the fuel pump) forms the upper closure of the fuel pump. Apart from the contact pins for the plug connection and the connections for the electric motor, the connector comprises a ground connection, inductances and capacitances for interference suppression, and carbon brushes for the electric motor. The carbon brushes, which are arranged in separate receptacles in the bearing plate, each make contact with the connector via a braid. The individual components of the connector are connected to one another either by plug connections, weld points or solder points. Since the fuel pump is arranged in the fuel tank, fuel flows around the connector. Fuels are corrosive media, which attack the connecting points of the connector. Particularly if the fuel contains methanol or ethanol, the connecting points are attacked in such a manner that they are destroyed in the long term, thus leading to failing of the fuel pump.
The invention is based on the object of providing a connector for a fuel pump which is arranged in a fuel tank and whose life is independent of the fuel used. It is intended to be possible to produce such a connector in a simple manner and economically.
According to the invention, the object is achieved by the features of claim 1. Advantageous refinements are described in the dependent claims.
The object is achieved in that parts of the connector, in particular the connecting points, are extrusion coated with plastic. This means that the connecting points no longer come into contact with the fuel, and are thus protected against long-term destruction by the corrosive components of the fuel. The advantage of the connector according to the invention is that extrusion coating with plastic is very economical, and the connector is thus effectively protected without any major cost.
It is advantageous to extrusion coat only individual regions of the connector. This reduces the amount of material used for extrusion coating. In consequence, the volume of the connector is not unnecessarily increased, so that the connector is physically relatively small. Furthermore, it is possible to exploit the advantages of a connector around which fuel flows. It is thus advantageous not to extrusion coat the inductances. Excessive heating of the inductances is prevented by fuel flowing around them during operation of the fuel pump.
In the same way, the capacitor need not be extrusion coated since it already has a fuel-resistant sheath. In another advantageous refinement, the capacitor is extrusion coated. This allows the use of a capacitor which is not sheathed, and is thus less expensive. In consequence, the connector according to the invention can be produced economically.
The braids of the carbon brushes are welded to the connector. In order to protect the connecting points, they and a portion of the braids are likewise extrusion coated with plastic. During the spraying process, the plastic is applied at a very high pressure in order to ensure that the plastic, which is made to be fluid for this process, fills the entire spraying tool, thus achieving high reproduction accuracy. However, since the plastic is at high pressure, there is a risk that it will penetrate into the braid. Sharp edges can be formed between the individual wires in the braid by the plastic which has penetrated into them and has solidified. This results in a precise bending point so that, if the braid is subjected to long-term bending stress, this can lead to the individual wires being broken. This damage to the braid can lead to the braid fracturing. This risk is advantageously avoided in that the braid is mechanically compressed in the region to be extrusion coated. This compression process reduces the size of the cavities between the wires in the braid, so that no plastic can penetrate into them.
In another advantageous refinement, the braids can also be extrusion coated without mechanical compression, if the braids are surrounded by a fuel-resistant sealing element in the region of the edge of the plastic. This sealing element may, for example, be a metal sleeve.
However, surprisingly, it has been found that it is sufficient to extrusion coat the braids even without any mechanical compression or sealing element, since the braid is mainly moved only during installation and only a small amount of movement capability is required throughout the life of the fuel pump arising from the wear resulting from the repositioning of the carbon brushes which are connected to it.
It has been found to be particularly advantageous to use polyoxymethylene as the plastic for extrusion coating.
In a further advantageous refinement, the extrusion-coated plastic is formed in such a way that it has forming elements. These forming elements may be latching and connecting elements or sealing surfaces of the plug connection, or else holding elements. These forming elements also allow automatic assembly of the connector with the bearing plate.
The ground contact is advantageously a metal spring, which is likewise extrusion coated with plastic at its connecting point to the connector.